1. Technical Field
The present invention relates to an antenna that is located at the end of a wireless communication system, or other radio system, and more particularly, to a wideband planar antenna having linear and circular polarization, which uses different polarization for transmission and reception to increase the isolation between transmission and reception by suggesting and using a type of a radiation element.
2. Related Art
A dish antenna is commonly used for a satellite communication service because the dish antenna has a simple structure and it can easily form dual circular polarization. Dish antennas are sometimes cumbersome due to their bulkiness. For this reason, various kinds of planar array antennas with a low height have been introduced. However, most planar antennas can only utilize one of linear and circular polarization, not both.
This characteristic limits the use of the planar antenna such that the antenna cannot be used for both transmission and reception. In most cases, planar array antennas for satellite communication are used only for the purpose of reception.
I have found that there are disadvantages to current dish antennas and current planar antennas. Efforts have been made to improve antennas.
Exemplars of recent efforts in the art include U.S. Pat. No. 4,475,107 for CIRCULARLY POLARIZED MICROSTRIP LINE ANTENNA issued on Oct. 2, 1984 to Makimoto et al., U.S. Pat. No. 4,816,835 for PLANAR ANTENNA WITH PATCH ELEMENTS issued on Mar. 28, 1989 to Abiko et al., U.S. Pat. No. 4,614,947 for PLANNER HIGH-FREQUENCY ANTENNA HAVING A NETWORK OF FULLY SUSPENDED-SUBSTRATE MICROSTRIP TRANSMISSION LINES issued on Sep. 30, 1986 to Rammos, U.S. Pat. No. 6,166,701 for DUAL POLARIZATION ANTENNA ARRAY WITH RADIATIN SLOTS AND NOTCH DIPOLE ELEMENTS SHARING A COMMON APERTURE issued on Dec. 26, 2000 to Park et al., U.S. Pat. No. 5,241,321 for DUAL FREQUENCY CIRCULARLY POLARIZED MICROWAVE ANTENNA issued on Aug. 31, 1993 to Tsao, U.S. Pat. No. 6,107,956 for AUTOMOTIVE FORWARD LOOKING SENSOR ARCHITECTURE issued on Aug. 22, 2000 to Russell et al., U.S. Pat. No. 4,922,263 for PLATE ANTENNA WITH DOUBLE CROSSED POLARIZATIONS issued on May 1, 1990 to Dubost et al., U.S. Pat. No. 5,005,019 for ELECTROMAGNETICALLY COUPLED PRINTED-CIRCUIT ANTENNAS HAVING PATCHES OR SLOTS CAPACITIVELY COUPLED TO FEEDLINES issued on Apr. 2, 1991 to Zaghloul et al., and U.S. Pat. No. 5,321,411 for PLANAR ANTENNA FOR LINEARLY POLARIZED WAVES issued on Jun. 14, 1994 to Tsukamoto et al.
While these recent efforts provide advantages, I note that they fail to adequately provide an improved planar anntenna having linear and circular polarization.